One of my favorite aspects of astronomy is how it tackles the biggest questions we humans have. How did this all begin? What is the ultimate fate of the Universe?

Are we alone?

Oh, that last one. Such an interesting question, and one that for centuries has been essentially unanswerable due to a lack of solid data. But that’s changed very recently. We’ve started exploring other planets up close. We’ve been able to listen to potential signals from other civilizations. And we’ve begun to get a handle on how many habitable planets there might be in the Universe.

I’ll note this is an opinion piece, but it’s based on the best data I know about these three avenues of inquiry: physical inspection of other worlds in our solar system, listening for E.T., and observing planets around other stars. Given the current state-of-the-art, and where these programs are going, I predict which of these three I think will pay off first – assuming life is out there to find.

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Due to the BBC bureaucracy, UK readers are not allowed to read your article as it comes under the BBC World Service. I had to switch to an overseas IP proxy address before I could read it.
The BBC does the opposite for overseas readers, editing what they can see on the UK site, so they have to switch to a UK IP proxy address. What a nuisance!

Assume for a moment that humans make it past our current self-destructive period and manage to survive long enough to reach out into space an colonize other worlds…..

At that point we will be able to say with absolute certainty that yes, there is other life in the universe.

So, IF we are alone in the universe today, that just means that we’ve yet to spread life to other places.

Not saying we ARE alone, only that if we look past today and into the future, we should be able to answer the question with certainty.

Anyway…..

On an unrelated note, I know you like to post cool timelapse videos occasionally. There’s a new site that finds the latest great timelapse videos and puts them all in one place – timelapse.org. They are broken down into categories, so it’s fairly easy to find what you want: http://timelapse.org/subjects/night-sky/

The Fermi Paradox is a paradox if you grant its premises – but those are heroic premises. The Wikipedia article has a number of responses to the paradox, but at a more fundamental level, I’ve never thought it was a meaningful paradox. The supposed paradox rests on a number of unfounded assumptions about the nature and behavior of alien life. It assumes, for one thing, that intelligent alien life and the technology it uses will take a form that we can readily recognize as such. It also assumes that such life, or at least its technology, will inevitably spread throughout all available space, such that we should expect to encounter it in our remote arm of the galaxy.

You may well be right, “that simple life is common, but more advanced multicellular life is very, very rare,” but I don’t think we have enough evidence to make even an educated guess on how common life is, one way or the other.

I can think of many reasons. Say advanced life doesn’t use broad emissions of radio waves to communicate. We’d never detect our neighbors. Humans themselves are starting to go dark, using fiber optic or tight beam radio rather than broadcast.

Or perhaps life has not had the necessary time to spread. Ever if another intelligent civilization formed earlier than humans by hundreds of millions of years, it may not have saturated much more than the local region around its home system by now. It could have spread around the galaxy in this amount of time, but only if it were willing both to devote many of its resources simply to expansion and to go out of reasonable contact range with some parts of its species. I can imagine that humans, once they have a solid 20 inhabitable worlds, wouldn’t be expanding all that fast because of a desire to stay within a century or so of communication distance with each other. That leaves little isolated pockets of civilization that humanity simply may not be near.

Or perhaps worlds similar enough to one’s home planet to be naturally inhabitable are prohibitively rare and terraforming is necessarily a very long, slow process, meaning expansion is just slow and expensive as hell. Or perhaps all worlds that one might be able to terraform are already inhabited, and species that reach this stage necessarily have the ethics to make them unwilling to wipe out native life in order to make the planet suit themselves and are unwilling to interfere with the evolution of life even on those few planets they could inhabit without terraforming. This would make expansion less compelling, since if one wants to live on a space station or a contained ground living station, it might as well circle the home planet or be on a Mars equivalent.

The problem with most responses to the Fermi Paradox is (especially the social ones) that they have to apply to ALL extraterrestial life. Just one extraterrestial civ who wants to expand rapidly ….

If you say that maybe they just hadn’t had enough time because they only evolved a hundred million years ago, then you are actually coming down on the “they are few and far in between”-side.

If they were very common, they would have been common a few billion years ago and should have (easily!!) spread everywhere by now.

Maybe it is much harder to cross interstellar space than we think, but unless that is the case, the Fermi Paradox is a pretty strong argument against a galaxy teaming with hundreds of extraterrestial civilizations.

I’m using a UK proxy IP and see the piece just fine. It’s my understanding that the majority of BBC services are funded by the license fee, but that the World Service is funded via the Foreign Ministry budget. I take it that is supposed to be the reason for blocking access per region.

Seems to me that life ought to exist anywhere and everywhere conditions allow it. How advanced that life actually becomes depends on local conditions. If there’s evolutionary pressure toward complexity, then complexity will happen. Life, though, changes the mix, so a planet on which life evolves to the complexity of, say, small snails, might never generate the evolutionary pressures that would lead to more advanced life. Just happy snails forever, or until something really big happened to stir the pot. Then, you might eventually get intelligence or you might get a dead, sterile planet. I don’t see any rule that says life aways moves in the direction of complexity and intelligence. Stuff happens.

Fermi Paradox: If we accept that you can’t travel faster than light, the odds of our being visited are vanishingly small. I think it is very,very difficult to make the case to send vessels out searching for other examples of intelligent life when you don’t know where they are and when it takes so freakin’ long to get anywhere.

On the other hand, if there is a way to get around the light barrier, then the creatures that manage that are likely so much in advance of us humans that they’d have little reason to spend time with us. Consider: A few quasi-Neolithic communities still exist on this planet. We have the means to visit them. But, except for a very, very, few, we all choose to go somewhere else more interesting. For all we know, Earth may have been given protected status after being discovered by some alien researchers. You know, like we try to protect the bonobos. (Seriously, if aliens are scooting about the galaxy at FTL speeds, I wouldn’t be surprised if their intelligence is to our intelligence as ours is to bonobos.)

Phil, next time you write one of these BBC articles could you ask them to publish it so both UK and everyone else can see it. There is nothing in your articles that is proprietary or insulting to the Queen. It is beyond silly that it is being censored like that. It probably makes sense to ad executives, and I’ve seen it explained a few times, but I still can’t comprehend it.

That’s the thing. I would call “hundreds” a galaxy “teeming” with civilizations, even if they aren’t very far from their home worlds, or are still on their homeworlds. Yes, it only takes 1 civilization that decides to devote itself to expansion, but there’s no reason to think that any of these hundreds of civilizations would make that decision if it’s horrendously expensive or for all the reasons like not wanting to wipe out native life or get out of contact with the rest of the species.

There’s also good reason to think that intelligent life couldn’t be billions of years old. Stars that formed much before the Sun almost never had Sun-like metal densities, which makes complex life impossible, meaning that even a civilization that makes the “reckless expansion” decision could still be plugging along a hundred million years in as we speak.

In order to cross the Milky Way in less than, say, 100 million years, each step of expansion has to take no more than, say, a hundred thousand years (if you’re going to have a world every 100 light years or so before setting out to terraform a new one). I find it highly implausible that you could take a planet from lifelessness to habitability in just one hundred thousand years. For humans, you’d have to get the “Oxygen Catastrophe” to happen first (among other things), something that happens on a hundreds of millions of years timescale.

@sebastian — it’s quite possible you are correct, and of course it depends on what you mean by “rare.”

Let’s put it this way: to get any kind of multicellular life at all, you need at least one generation of stars to grow old and go nova. OK, that puts the earliest life anywhere in the universe at around 200 million years after the Big Bang or thereabouts. Maybe later.

So you need heavy elements and another generation of stars and planets. We’re now a billion or so years in. So you’d expect the very first living things to appear somewhere around then — give approximately 12 billion years ago, making some pretty generous assumptions. A couple of generations of stars have turned to white dwarfs since then. And some small percentage of them might have had living things. Maybe civilizations, even. But if they all lived and died billions of years ago we would never see or hear them.

Now, it’s possible to conceive of a galaxy-spanning civilization that engages in wide-scale galacto-engineering. But even making generous assumptions for when they arose and could make their schemes manifest, we might not see the effects yet, since if they worked on a galaxy 500 million years ago and the galaxy in question is 250 million light years away there hasn’t been enough time. Assuming we even knew what to look for.

In our own galaxy, you’d expect that say, one in a million stars has a civilization, but even at higher numbers it’s not hard to see that a bunch of things have to come together for us to be able to see another civ. If they were 100,000 light years away and blasted a signal nice and loud right to us that lasted 10,000 years, but did it so that it stopped (from our perspective) 100 years ago, well, we’re SOL on finding them. So you could have thousands of civilizations in a galaxy that would never know about each other unless a lot of them were around each other in kind of a narrow time frame. Even a Dyson sphere wouldn’t necessarily be obvious from a great distance away.

The Fermi paradox is assumptions built on top of questions built on top of guesses. We have a few possibilities:

Life is just here on Earth, for whatever special reason. Unless you want to invoke one or more gods, odds are that other planets approximate the same conditions, age, etc, and likely have some form of life at the very least, and that doesn’t even include the possibilities of other exotic forms of life that we may not even have considered yet.

Advanced life is just here on Earth, for whatever special reason. This definitely has more going for it in the science realm, since we don’t know exactly why life has advanced (and been destroyed) here so many times. The moon, the arrangement of heavy planets in the stellar system, cosmic rays, some as yet unknown cause, etc. Still, though, given the number of planets and stellar systems out there, likely the conditions for advanced life have been met many, many times.

Advanced life may also exist elsewhere, but either a) hasn’t communicated, b) is too far away to communicate, even accidentally like us sending out radio waves, or c) has communicated, accidentally or intentionally, and we just missed it because the sky is so huge and we don’t know how they were trying to communicate. These, I think, are the most likely. Just because the neighbor hasn’t said hi, hasn’t shouted it in a way we’d understand, or hasn’t said it while looking at us, doesn’t mean they aren’t there.

In the U.S., half of our society cannot even communicate with the other half.
Half of our people deny the existence of climate change and evolution.

Most people won’t even recognise intelligent life as intelligent life. Communication with them will be impossible. Nothing we say will make sense to them and we will refuse to understand anything they say.

If you live in the UK, as I do, and want to read Phil’s article then use a proxy service such as http://anonymouse.org which will pretend to the idiots at the bbc that you reside elsewhere, and let you view what the rest of the world can see.

I’m surprised, Phil, that you didn’t mention something that I’ve always thought would be a little problem if we did discover life on Mars. (Though maybe I’m wrong about this being a problem — please tell me if I am.)

So, there’s been transfer between Earth and Mars, right? Like, we find Martian rocks in Antarctica, no? So, if we were to discover evidence on life on Mars, would we be able to tell right away if it had a separate genesis from life on Earth? I mean, sure, it would be massively cool and interesting and scientifically useful if we discovered evidence of life on Mars, but the real question — at least in the context of your essay — is, How easily does life arise? Right? So if there was only one genesis in our solar system, and Mars seeded Earth or vice versa, that wouldn’t answer that question, would it?

(FYI, I was able to read the BBC piece via both US and UK IP addresses.)

@9. sebastian
“The problem with most responses to the Fermi Paradox is (especially the social ones) that they have to apply to ALL extraterrestial life. Just one extraterrestial civ who wants to expand rapidly”

There’s a sample bias at work. If you’ve ever looked at the Pale Blue Dot, you’d see that we are a very, VERY small target. And that was from the Solar System’s front yard, light-years short of our next-door neighbor. Now, consider that the universe is huge. Really, REALLY huge. If an interstellar species started off from tens of millions of light-years away, forget the time it’d take to get to us; odds are darn near 100% they didn’t even head vaguely in our direction. It took billions of years just to get microbial life started on Population I stars. We haven’t even gotten past the Moon and we’re going to hold these aliens to some sort of expectation that they’re obligated to drop by??

The Fermi paradox considers these aliens traveling between stars at speeds attainable with current Earth technology, but assumes they would head to Earth entirely for our convenience and hides this arrogance in “but if it’s so common there MUST be SOMEONE willing to go through the trouble” fallacy. In other words, we’re assuming that a species would be smart enough to travel the stars, but stupid or bored enough to dive deep into a gravity well just to say hi to a bunch of idiots who haven’t even visited a nearby planet? And the only “logical” argument is a completely hypothetical sample size? I get the “you can’t predict alien behavior” angle, except you can to an extent. I don’t know anyone I consider intelligent to DELIBERATELY regress and try to communicate with other humans using grunts (except as a joke), but that’s pretty much what we’re asking of this hypothetical alien species. From the outside looking in, we are a small, insignificant target and the idea that there’s anything on Earth worth visiting (especially us) is rather silly.

It’s subtle, but the Fermi Paradox makes an obscenely arrogant assumption that a civilization advanced enough to travel the stars would need or even be vaguely interested in Earth. If you can travel between stars for millions of years, you really don’t need planets anymore, let alone be interested in them. If we’re the 97,468th “Goldilocks Zone” planet these aliens have seen and they’ve lived without a home planet for 10,000 generations. . . what exactly makes Earth interesting? Us? To quote Niel deGrasse Tyson: “We’d be blithering, drooling idiots to them! When’s the last time you had a conversation with a worm?” Then consider the trouble it’d be to approach Earth. (It’d be rather tricky to position a huge craft capable of sustaining a civilization without a planet within observation distance of Earth. There’s massive deceleration — killing all whatever interstellar velocity the craft had built up until then — required to dive into the Sun’s gravity well without zipping past the Earth.) Would you be willing to travel a thousand miles and then through rush-hour traffic just to chat with a worm just because that worm thinks it’s special?

If life is special, then odds are very slim someone has found us by now. But consider that life IS common, especially intelligent life. A spacecraft could’ve passed within the orbit of Neptune, saw one “meh” planet filled with idiots and moved on without ever having been detected, essentially as Bill Watterson predicted. I’ll admit that makes a lot of assumptions, but the assumptions are no more outlandish than the Fermi Paradox itself.

Maybe it is much harder to cross interstellar space than we think, but unless that is the case, the Fermi Paradox is a pretty strong argument against a galaxy teaming with hundreds of extraterrestial civilizations.

I think that may be the answer. Interstellar travel – even of small probes – is really, really difficult in terms of engineering. You’re always faced with a dilemma when designing starships, in that you either

1. Need to go really fast, which consumes staggering amounts of energy and requires systems that can use it to create useful acceleration/deceleration. Systems which are really only hypothetical at this point – we know virtually nothing about difficulties that engineering them might entail.

OR

2. You need to spend a very long time (centuries or thousands of years) in open interstellar space in transit. Think of how difficult it is to engineer machines to last decades on Earth, and then imagine trying to make a far more complex machine that can function longer than, say, agricultural civilization on Earth, and deal with any mechanical problems that may arise in complete isolation and no alternative power supply except nuclear reactors. I’m skeptical that it’s even possible to do that.

Honestly, doing either of them may simply be impossible in engineering terms, in that you can’t engineer a starship that will move fast enough or survive long enough in interstellar space to get to the other solar system and do its mission. I’m hoping that’s not true, but it’s certainly a possibility – and it would explain most of the Fermi Paradox very well.

Back on the issue of intelligent life-

I wonder if cultural fragmentation might be another issue keeping civilizations from expanding across interstellar distances, assuming it’s possible. Go beyond a few dozen light-years from your homeworld, and the communication lags are so big that any civilization composed of non-immortal beings is probably going to fragment into different civilizations.

Unless we are lucky* on Mars, the current mission prepares for sample return (SR). But on Earth it takes many trips for paleontologists to find the fossil bearing layers, or for microbiologists to learn how to grow a few species to study them. So realistically we need tens of missions to find or exclude extant or extinct life.

With the current rate of missions, that means decades or centuries. Meanwhile, astrobiologists claim that exoplanet research can net an observation of an inhabited terrestrial in 1-2 decades.

Let us check how they fare. IIRC they predicted 2010 that the first habitable Earth analog (terrestrial with radius ~ Mars = 0.66), 3 out of 4 known ages are greater than Earths, meaning that they have had enough time to form an oxygenated atmosphere.

——————
* I do suggest we should always do an end run on life in the system, considering the many costly and time consuming (but data yielding!) sample return likely needed. For theoretical and now practical reasons, RNA was likely selected for in the primordial anoxic and iron filled environment where it seems to work best as an enzyme.

So we should always look for nucleotides and their heteromers. Unfortunately they don’t fossilize well, so it would be a test of extant life. The SOLID instrument does this.

Because it is too loosely constrained to be useful, same as for the last factors in Drake’s equation where it goes from inhabited (detectable oxygen atmospheres after a few billion years) to ETI (complex multicellulars, linguistic intelligence et cetera) planets.

Due to lightspeed constraints, where seems to be only two feasible economies out there. Information barter and colonization.

– Information barter economy feasibility revolves around narrowcast and short distances, it will be rare and local.

– Colonization grows naturally from the system out to the Oort cloud bodies, which on an exponential scale of economical progress is the large step. Once you are there, it is costly and risky to redevelop the technology to go back down gravity wells, if it can be done at all (doubtful).

So these migration waves will scatter in the Oort clouds between the stars. At the same time they will be radio and artifact silent. Hence the galaxy can be colonized on a time scale on the order of the current age of the universe, and we may never know.

If you claim that this is unlikely, the mere existence of such a scenario shows that the FP/full DE is ill posed vs possible observations. They are testable theories (in that positive observations work), but they can’t be used to construe “a paradox”.

#18:

There can never be “civilizations” over interstellar scales, the economics are forbidding. Migration waves would be natural, but of course the different migrants will evolve into different species in very short times (geologically speaking).

Population genetics predict that you need one crossbreeding/generation to keep biological species as a coherent population. It can happen in the inner system but it is unlikely already for the Oort clouds. Even if you imagine a forbiddingly expensive scifi “generation ship” between planets in different systems, as you hear from the name they will not mitigate speciation effects. Eventually the planets will separate biologically, and the interest to keep traveling in between will flag.

But why planets!? I believe it is considered today because planets are more romantic biospheres. But when and if colonization takes off, it will most likely be spreading from body to body as similar “infections” always do. Most habitable bodies aren’t planets, something that will inevitably play into what will happen.

Oops. The first of my comments is an unintelligible C&P, which I didn’t catch in time to edit it.

I was noting that the year after (2011) the prediction (2010, IIRC) 2 Earth analogs (defined as habitables with radius between 0.5 – 2 Earth radius) were observed. And really 2010 the recently accepted Gliese 581 g was seen. So they did good on the prediction.

The rest was a note on observability, that astrobiologists will need a new generation observatories after JWST but one such would suffice, and that we generally see old enough planets to observe oxygen.

And when I say “Most habitable bodies aren’t planets” in the 2nd comment, I mean habitable in the technological sense, which is a different sense than in the first comment natch.

The fact that interstellar travel is going to be quite difficult no matter how you slice it means that any civilization really interested in expanding rapidly is going to have to be very good at making spaceships. And if they are that good at making spaceships, it seems to me quite likely that they will rather automatically end up having to value habitable planets much less. The same technology that will allow them to mount vast interstellar expeditions will also allow them to cut the umbilical that ties an intelligent species to a planet at all.

And that would probably make them much harder for a planet-bound civilization such as ourselves to recognize. They could be out there right now all around us, silently gliding in their habitat-spaceships between the stars, or even right here in our solar system, drifting in the Kuiper Belt, and we might not notice them or recognize them.

Another thing to consider is that, even if it doesn’t take that long, cosmically, for an expansionist civilization to spread throughout the galaxy, how long would such a civilization exist in a galaxy-spanning state? Total extinction would not even be necessary – smaller scale collapses back down to isolated pockets of colonization would be enough. If the period of galaxy-spanning hegemony were relatively short compared to the periods of collapse and any subsequent recovery and the periods of initial and re-expansions, then it becomes more likely that in our current slice of time, we on earth here exist in one of those in-between times, with our region of space empty.

There is absolutely one thing that we can predict about the behavior of intelligent alien life – they are going to act on the grand scale in their own best interest. While they may (indeed likely will) have all sorts of play and altruistic behaviors as well, which may be so varied that we cannot even predict them, it can be fairly certain that all of these unpredictable non-self interest behaviors will be small scale relative to their total economic capacity.

Because any living thing that devotes a large scale of its economic capacity to things that do not promote its own self-interest does not survive for very long.

And we must ask ourselves, what does mounting an interstellar expedition to colonize earth/contact earthlings do for a alien intelligence’s self interest? And once you think about it for a while, the answer pretty much becomes “not much at all”. It is far easier to see self-interest getting them to this solar system, but far harder to envision them making the special effort once having arrived of making themselves known to us here on earth. If they’re going to be interested in any of the planets at all, rather than hang out in the Oort cloud and Kuiper belt (which does raise the interesting question of whether or not we could develop soon the technology necessary to detect alien activity in the Kuiper Belt or Oort cloud, as an extension of what we’re currently doing studying and searching for KBOs), it will probably be Jupiter.

So the scenarios for contact would be:

1) Aliens contact with us as a major undertaking with self-interest in mind. This would imply something specially valuable about us here on earth, and the only way I see this being likely is if habitable planets and intelligent life is rare, and we are one of the rare, interesting examples. But of course this makes it not that likely that one of the other rare, interesting examples just happens to be close enough to contact us! (And would we want such a contact – if they are seeking us out for their own self interest, well the one thing we can certainly predict about their motives is that they are going to value their own survival over ours….)

2) Aliens contact us as a major undertaking that is not motivated by self-interest. One could envision contact being attempted due to religious motivation, or the whim of a dictatorial ruling class or individual, or something like that. But by definition such an endeavor counter to self-interest is self-destructive, and we would not expect such civilizations to survive making too many such attempts. Which means we would only be contacted if we were lucky/unlucky enough to be one of their very first or even only such attempts, which would require them to be really close to us to begin with.

3) Aliens contact us as a minor undertaking that is not motivated by self-interest, but rather as the result of accident or play or altruism or something like that. This of course, requires the alien civilization to reach a level of advancement so immense that an interstellar mission becomes a minor, trivial undertaking for them. And that is asking for a LOT in terms of their advancement, and the accompanying need for time to reach that level and resources to maintain such a level.

The most likely habitat for extant life on Mars is deep in the lithosphere. That would mean that while a positive finding in the near future missions would of course prove its existence, a negative finding does not rule it out.

Indeed in this situation, to rule out life on Mars could probably not be done until a very large and permanent human population is established on the surface – the kind of population that would support extensive mining and digging deep into the subsurface.

“The basic SETI assumption is that aliens are out there and want to contact us”

Yes. And that is why it is just silly and will likely fail. WHY would they do this? Our RF leakage gets faint after a few light-years and with every passing year it gets fainter and fainter as we rely on fiber for long haul data and low power RF for local data and hardlines for the rest. The days of the multi megawatt AM radio that you could hear all across the nation after dark are pretty much over.

Ohhhhh….we’re SO special that ET is trying to contact us. LOL. Keep wasting time at the “watering hole” boys.

I think it is at least 50:50 that the first alien biological atmospheric signal detection will be on Mars, with methane.

Good point, amphiox! I would only add one caveat that, being a regular here, I’m sure you already know, and that is, it’s still debatable whether or not ANY methane (biologically or geologically-produced) truly exists in the Martian atmosphere. Phil has mentioned the need for more statistically-significant detection results, and other influentials like Zahnle at Ames have expressed rather vehement doubts about the findings to date.

Anyway, hopefully we’ll know better in the next few weeks when Curiosity’s atmosphere “sniffer” is activated.

One of the problems I always have with arguments in favor of finding other intelligent life has to do with intelligence itself.

Arguments in favor of abundant intelligences seem, in my opinion, to overrate the evolutionary value of intelligence, at least the way we exemplify it. The assumption seems to be that intelligence is somehow a successful long term evolutionary strategy, and frankly, I think that is questionable. Homo sapiens has only been around a few eye-blinks relative to the grand scale of time, and right now we don’t seem to be heading in a very good direction as far as sustainability goes. The various dinosauria and other “dumb” species made if for millions, even hundreds of millions of years compared to a hundred thousand or so for humans.

So which is the better evolutionary strategy that you’d see more of throughout a galaxy teeming with life?

The various dinosauria and other “dumb” species made if for millions, even hundreds of millions of years compared to a hundred thousand or so for humans.

An apples to oranges comparison, and a highly unfair one at that. Dinosaurs are an entire clade of organisms, humans just one species. The fair comparison is Dinosaurs versus mammals, and then its a dead heat (including birds as dinosaurs, of course).

So which is the better evolutionary strategy that you’d see more of throughout a galaxy teeming with life?

Well, first of all, you must have non-intelligent life before you can have intelligent life. As one must arise from the other, that means that the initial frequency of the first MUST be less than the second.

However, technological intelligence expands the potential habitat for life. Technological organisms are not limited to “habitable” worlds. They could conceivably colonize many other habitats in the universe as well. Thus, IF large scale space colonization is possible, even if technological intelligence is initially rare and unlikely, once established it has the potential to spread further and faster than non-technological life.

Thus, even if individual intelligent species do turn out to have limited lifespans, all it takes is for enough intelligent species to last just long enough to colonize another world before going extinct, and intelligence will spread. Intelligence thus becomes an evolutionary watershed, an adaption that increases evolvability. Much like photosynthesis, or adaption for living on land, or flight.

And that means that it might very well turn out that biospheres with technologically competent life are actually MORE common than biospheres without intelligence (with technological habitats, including spaceships, being included as biospheres). Because, barring non-directed panspermia, biospheres without intelligence can only arise spontaneously, while biospheres with intelligence may have the capacity to reproduce themselves, and spread exponentially.

If we look at earth, recognizably intelligent life has been around for about 10,000 years while the planet has had life for roughly 4 billion years or so. So if you were to just look at the earth, the odds of finding an intelligent being amongst all those life forms at any point in history is about 1 in 4 million. Using this reasoning, if we were to find a life-bearing planet somewhere, the odds that there would be intelligence would be lower (for earth, the odds are massively biased in our favor, since by definition we have to be on a planet with intelligent life.)

As such, even if life were rather common (an assumption for which we have absolutely no data… yet…) it wouldn’t surprise me if we were the only intelligent life form in the galaxy at this moment in time.

The days of the multi megawatt AM radio that you could hear all across the nation after dark are pretty much over.

However, narrow beam radio and lasers used for astronomical observations would continue, and would in fact be easier to detect than radio leakage, almost as easy to detect as an intentional beamed signal (though it would contain much less information).

Ohhhhh….we’re SO special that ET is trying to contact us. LOL. Keep wasting time at the “watering hole” boys.

Even if SETI is likely to fail, it is still worth doing, because 1) it costs virtually nothing to piggy-back it on top of regular astronomy that we would be doing anyways, 2) secondary benefits accrued to the development of technology 3) a positive result, even if unlikely, would be transformative, and 4) we currently aren’t capable of searching for intelligent life in any other way.

If we look at earth, recognizably intelligent life has been around for about 10,000 years while the planet has had life for roughly 4 billion years or so.

This isn’t a valid statistical extrapolation, from a sample size of one. One can just as easily argue that intelligent life is inevitable but it always takes approximately 4 billion years of evolution to produce, and thus every habitable planet older than 4 billion years is guaranteed to have a recognizably intelligent species about 10,000 years old.

To make a valid statistical argument, you actually have to find a second example of a technological intelligence, and at least one other example of a biosphere without an technological intelligence.

@37 “One can just as easily argue that intelligent life is inevitable but it always takes approximately 4 billion years of evolution to produce.”

This assumes that intelligence is some sort of necessary end product of evolution. From what I know of evolution I strongly doubt this. I see no reason barring dinosaurs from having evolved bigger brains millions of years earlier, they just didn’t…

Big brains are simply the result of a species being selected for a large gathering of nerves in one spot. Once you have nerves, this does not require any major evolutionary changes, simply the continual tweaking effects of natural selection. Nerves have been around for quite a while (worms, and other ‘simple’ animals have them.) Since nerves evolved, all the ingredients were there for a species to go down the evolutionary path of ‘more nerves.’ Whether circumstances were right for this to give an evolutionary advantage is mostly down to chance, and since this did not happen for a long time, I still argue that the odds of (high) intelligence giving an edge in survival are quite low.

You could say we have a sample size of 4 million (10,000 year slots) with only one positive hit.

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I can think of many reasons. Say advanced life doesn’t use broad emissions of radio waves to communicate. We’d never detect our neighbors. Humans themselves are starting to go dark, using fiber optic or tight beam radio rather than broadcast.

I’ll grant that fibre-optic comms will make the communication radio-dark, but “tight-beam” radio probably isn’t anywhere near as tight or as specific as you seem to think.

A simple dipole antenna emits rf in two very broad lobes. Dipoles and “long-wire” antennas are commly used for long-wave and medium-wave transmissions. There are four commonly-used antenna types for short wave and “upwards” (increasing frequency, which is the same as decresing wavelength) – a vertical (typically a loaded quarter-wave antenna), a dipole (typically a hlaf-wavelength), a Yagi-Uda, and a dish antenna. The first two are essentially omni-directional (not strictly true, but close enough for government work).

The Yagi-Uda is a refinement of the dipole, in which a reflector and one or more director elements alter the radiation pattern of the dipole. The more elements the Yagi-Uda has, the more lobes it has, but also the ratio of the energy focussed in the main lobe to secondary lobes is larger. A 17-element Yagi, for example, confers about 24 – 30 dB of antenna gain, mean that the effective radiated power (ERP) from the main lobe is 2.4 – 3.0 logs (powers of 10) above what you would see emitted in that direction from a theoretical dipole antenna. This isn’t free energy, it is taken from emissions that would otherwise have left the antenna in other directions (i.e. the secondary lobes). The second-largest lobe of a Yagi antenna is out of the back of the antenna, so a substantial portion of the emitted signal actually leaves the antenna in the least desirable direction, but the side lobes also emit a non-trivial amount of rf energy. The plausible size of a Yagi antenna depends on the wavelength. Since the dipole element is typically a quarter-wavelength, this means a Yagi is unwieldy at wavelengths longer than about 10 m. At much shorter wavelengths (say, less than about 20 cm), the precision required to make the antenna elements the correct size and spacing becomes unfeasible (or at least, unfeasible with earthly technology). (Also, the nature of the rf changes as you edge from UHF into the microwave band.)

A dish is almost the ideal kind of antenna, but it requires a certain minimum diameter (I think about 1.5 wavelengths) in order to be better than a Yagi. The greater the diameter of the dish, in relation to the wavelength, the narrower the beam, and the greater the front-to-back ratio of the antenna. Most of the energy emitted from a dish antenna goes into its main lobe.

Wireless telegraphy will be around as long as we need communications without having to lay infrastructure through which to communicate. Satellite links, for instance, look likely always to be radio or microwave. Radio and television broadcasts are still widespread, and it’ll take an awful lot more fibre-optic cables before internet TV is a competitor for broadcast TV.

So, unless you are aware of some antenna technology that I am not, human communications activities are a long, long way from being radio-dark. And they look likely to remain so for the foreseeable future.

My opinion is that there is no life in the galaxy currently that travels between the stars. It’s been figured that self-replicating probes could spread throughout a galaxy the size of the Milky Way in about a half-million years.

They (or their probes, one of the two) would already be here, and not because they picked us out of a haystack, but because they’d be everywhere.

I would expect that there is still intelligent life in the Galactic Habitable Zone, if nowhere else, and that they are and will be stuck at home the way we are and will be.

RF leakage gets faint after a few light-years and with every passing year it gets fainter and fainter as we rely on fiber for long haul data and low power RF for local data and hardlines for the rest. The days of the multi megawatt AM radio that you could hear all across the nation after dark are pretty much over.

AFAICT, you seem to have confused your megawatts and kilowatts.

Multi-kilowatt AM stations are still around. It doesn’t take immense power to propagate a short-wave signal around the globe, because it will skip using the ionosphere. A kilowatt will do nicely. Of course, this also means that we’re beaming less energy into space, but the wave bands that get refracted in the ionosphere aren’t going to propagate outside Earth’s ionosphere very much anyway.

IIUC, the most powerful AM transmitter is the BBC World Service, which feeds about 500 kW into the antenna array. Also IIUC, it is still going.

However, even long-wave signals won’t get very far outside our atmosphere, because a substantial portion of these refracts around the Earth itself, so the rf power that escapes into space is small. What is more likely is that our TV, radar, and other VHF, UHF and SHF signals (that mostly pass straight through the ionosphere unaltered) are the signals that will be detected elsewhere, if anyone is listening.

The 1/r-squared law is an issue, of course, so radio leakage is unlikely to be a reliable means for detecting us or any other technological civilisation within more than (say) a hundred light-years.

This assumes that intelligence is some sort of necessary end product of evolution. From what I know of evolution I strongly doubt this. I see no reason barring dinosaurs from having evolved bigger brains millions of years earlier, they just didn’t…

No, actually it doesn’t. It just assumes that intelligence is a possible end product of evolution, which we know is true, as we are here.

Suppose that earth has produced 10 quadrillion species in 4 billion years, and out of those 10 quadrillion species only one, humans, were technological. What that does tell us about the likelihood of technological intelligence on other planets?

It tells us nothing. Because the denominators are different, and we don’t know how many species an average habitable planet will evolve. So even if the odds on earth are 1 in 10 quadrillion, if the average habitable planet will routinely produce a few quadrillion species, then the odds that any individual habitable planet will produce an intelligent species rapidly rises to unity. Even more so if earth turns out to be a lower-end outlier in terms of fecundity and the average habitable planet actually produces more species than earth has.

There is absolutely no need for any “necessary” trajectory towards evolution of intelligence (there isn’t). It’s all the statistics of large numbers.

You could say we have a sample size of 4 million (10,000 year slots) with only one positive hit.

Yes, but again, you cannot extrapolate from this number to an estimate of the likelihood of intelligent life on other planets because, again, the denominators are different, and we do not know how many slots other habitable planets are likely to have.

Also, these individual slots do not have the same likelihood of being a positive hit. The first few million slots actually has a very low likelihood, approaching zero, for the simple matter that it takes time to evolve the preadaptions that make intelligence possible. The later slots actually have an increasing likelihood of being a positive hit. The positive hit likelihood will then peak for a period, and then decline again as the habitable biosphere ages and habitability drops.

We also do not know what effect the first positive hit will have on the subsequent likelihood of future hits. We don’t know how long a technological intelligence is likely to last, after its first appearance. We don’t know if technological intelligences are likely to produce other new technological intelligences, by uplifting domestic species or by developing machine intelligence. And if a technological intelligence goes extinct, it leaves artifacts behind, and we don’t know what effect those artifacts will have on promoting or impeding the evolution of another technological intelligence.

Here on earth, humans are the only technological intelligence, but we have many pre-technological intelligences. Among the synapsids at least three independent lineages (primates, cetaceans, elephants), among the amniotes, at least two (mammals and birds), among the animals, at least two (vertebrates and cephalopods), or perhaps three (if you think social insects have potential for evolving technological intelligence), and those three are distributed in all three of the major lineages of animals (deuteurostomes, ecdysozoa, and lophotrochozoa). In other words, every single major lineage after the evolution of nerve cells has, on earth, went on to produce examples of complex nervous systems at least theoretically capable of evolving intelligence if the right environmental opportunities and selection pressures arise. And we also know that those environmental and selection opportunities DO arise, because we are here.

If humans went extinct tomorrow, I would be very confident that a second technological intelligence will evolve again on earth some time before earth ceases to be habitable anymore. And I would bet good money that it would happen more than twice.

And these subsequent intelligences will have human artifacts in their environment, ready-made tools they can dig up, stumble upon, and use – rusted forks and knives, glass shards, plastic containers, pieces of concrete, already forged metals, and so forth.

Since nerves evolved, all the ingredients were there for a species to go down the evolutionary path of ‘more nerves.’

And the thing is, the fossil record shows that they DID go down the evolutionary path of “more nerves”. At least among the vertebrates, for which we have perserved skulls, from the first appearance, the maximum brain size of all species as rather steadily increased. The early dinosaurs had bigger brains on average than the reptiles and amphibians that preceded. The later dinosaurs had bigger brains on average than the earlier dinosaurs. The biggest brained dinosaurs, the troodontids, tyrannosaurs, and dromaeosaurs, produced their biggest brained members all in the late Cretaceous. These dinosaurs’ brains were small in comparison to the average of their later descendents, the birds. And the biggest brained birds are all modern species. The same trend is seen among the mammals. Almost every single lineage of mammals produced its brainiest known member after the paleocene, close to modern times. Even excluding humans from the equation, the modern biosphere is, on average, the most intelligent biosphere earth has ever seen.

Whether circumstances were right for this to give an evolutionary advantage is mostly down to chance, and since this did not happen for a long time, I still argue that the odds of (high) intelligence giving an edge in survival are quite low.

One can just as easily argue from this pattern that technological intelligence was not possible on earth before modern times, because the necessary preadaptions were not all in place, and that the steady increase in braininess of the brainiest species that we see in the fossil record indicates that an intelligent technological species only became possible on earth very close to modern times, the steady increase in the average brain size of the brainiest species crosses a critical threshold, and that, the moment it became possible, humans almost instantly appeared. It just takes that long before average brain size can evolve to something large enough that a technological intelligence is actually a possible evolutionary trajectory for any species.

And to say that high intelligence does not give an edge in survival flies in the face of all evidence. Humans are monstrously successful. Many of the other intelligent species on earth are also quit successful. And all the intelligent modern species that are not currently successful and endangered are endangered almost exclusively due to competition from humans, an even more intelligent species. If humans were not around, none of them would be in danger.

The rate-limiting step in the evolution of intelligence isn’t actually the utility of intelligence in the environment. Intelligence is a such a generalistic adaption that it is hard to imagine ANY environment where greater intelligence would not provide an advantage. The rate-limiting step is actually the metabolic cost of growing an ever bigger brain.

It’s been figured that self-replicating probes could spread throughout a galaxy the size of the Milky Way in about a half-million years.
They (or their probes, one of the two) would already be here, and not because they picked us out of a haystack, but because they’d be everywhere.

Here’s the thing to consider, though. IF these self-replicating probes WERE here, would we know? Could we detect them? If there were self-replicating probes or their remnants in the Oort Cloud, or Kuiper Belt, would we see them? If we saw them, would we recognize them as probes and not as KBOs?

What if they were closer, in the asteroid belt? Could we see them there? Could we distinguish them from regular asteroids there? Would we even be able to detect them if they were nano-scale and in orbit around the moon? Around earth?

Remember that the laws of physics would dictate that self-replicating probes, assuming self-replication was their primary function, would preferentially prefer to congregate in debris belts far away from gravity wells, regions like Oort clouds and Kuiper belts, rather than inner rocky planets like earth.

We must also not forget the possibility of niche exclusion when examining the biota of earth. Humans may be the only technological intelligence on earth not because technological intelligence is hard to evolve, but because humans have actively suppressed the evolution of other technological intelligences once we appeared on the scene.

To make a valid statistical argument, you actually have to find a second example of a technological intelligence, and at least one other example of a biosphere without an technological intelligence.

You can get around this in two ways, either model it as a stochastic process in which case you will be estimating a parameter instead of probabilities of events, or by making a toy model where you can average over worlds instead of events.

The 2nd is easier here, and PZ Myers did this one of his biology talks to get to the probability for something like us. What you do is that you observe that diversity is mainly recovered after mass extinctions. (And since then we now know the posterior diversity level will be independent of the prior, making the model constraint water tight.)

So let us look at such “world” analogs for land, because we now we have one ETI equivalent observation here (us). IIRC he put down two major mass extinctions, making 3 independent worlds. Thus the likelihood for ETIs is ~ 1/3 per habitable planet. (If given multicellularity, which is a big “if”.)

I don’t necessarily agree with this, but I find it interesting that we can model this and that the upper limit from observation is so high.

even if it doesn’t take that long, cosmically, for an expansionist civilization to spread throughout the galaxy

If we conservatively assume that they use volatiles for chemical rockets (say, by electrolyzing water ices) because that is what we know is possible on a sustained basis, a migration wave random walk in roughly 2D on the galactic disk would take on the order of the age of the universe unless I am mistaken. (Random walk because, as I have argued, they would not stay in contact.)

If someone would have got started with the early star generations, and we now know metallicity isn’t a problem for making terrestrials, they would be about spread out now. Or it would take a few billion years to get started, and the coverage would be local as of yet.

@ 42:

It’s been figured that self-replicating probes could spread throughout a galaxy the size of the Milky Way in about a half-million years.

There is, as of yet, no technology for “self-replicating probes”.

Life is pretty efficient that way but it takes a lot of resources anyway – a growing cell uses ~ 10^6 times as much energy as minimum survivability. Either you have to lug around a large biosphere (as when you colonize) or use time to evolve a new one from a few cellular species (analogous to when you terraform).

So based on what best technology is capable of I would say forget it, utopian dreams have never made it to reality.

@44 “So even if the odds on earth are 1 in 10 quadrillion, if the average habitable planet will routinely produce a few quadrillion species, then the odds that any individual habitable planet will produce an intelligent species rapidly rises to unity. ”

You’re assuming an intelligent species will never go extinct. All other species go extinct, I’m not convinced our intelligence will exempt us from that.

And if the odds are 1 in 10 quadrillion species, if you were to visit an average planet now, then the odds that all those billions of species will have an intelligent species at that moment are still quite low. You’re confusing ‘will evolve’ (which you claim is close to unity if you’re patient enough) with ‘has evolved.’

Assume a constant rate of star/planet formation, and let’s say, for the sake of argument, that the galaxy is churning out exact copies of the Earth at a constant rate. Then if we were to randomly visit one of these Earth clones the odds are going to be quite low that it is exactly the 4 billion years old it needs to be for intelligent life to be found on the surface.

And if a technological intelligence goes extinct, it leaves artifacts behind, and we don’t know what effect those artifacts will have on promoting or impeding the evolution of another technological intelligence.

One thing we do know is that our technological society has used up all of the most easily-accessible resources in developing technology from stone tools to indudstrialisation. For example, the extraction of iron ore now requires technology, as our forebears left so little of the easily-available stuff lying around.

Therefore, if our technological society becomes extinct, we have hindered the potential development of any successor technological society.

It seems reasonable to assume that a similar effect will pertain elsewhere, if technological societies have risen and gone extinct on other planets.

Intelligence is a such a generalistic adaption that it is hard to imagine ANY environment where greater intelligence would not provide an advantage.

It is not hard. Any environment in which the nature of the selection pressures is constant will tend to develop highly successful specialists. Intelligence is most valuable to generalists in a changing environment.

Something that I have not seen mentioned in this thread so far is how to recognise life. With the millions of known species on Earth, we find it difficult to come up with a definition that includes everything we consider life and excludes everything we consider not to be life. Probably the best definition I have seen to date is something along the lines of “any organised system that undergoes Darwinian evolution”, but I think people have still managed to find exceptions to this.

There is (IIUC) still debate about whether viruses should be counted as alive or not.

If an alien life form were to possess a radically different biochemistry from us, how would we recognise it?

After watching this, I just have one thing to say to DaeSung…”GET SOMEEE!“

Also, if you missed SBS Big Show, you can rewatch the Tonight, What Is Right, and Cafe performances on Big Bang’s official Youtube channel.

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JT’s 4th Mini-album Big Bang VNbig bang
thoughts
I’m really impressed with this mini-album. It shows how much BB has grown in 2 years they’ve been away. I have to say, this whole mini-album was very J-Pop influenced, well considering “Hands Up” and “Somebody to Love” were originally Japanese songs.

Yes, Cafe deserves it’s own paragraph. Cafe is really an amazing song. It’s like there’s a bunch of upbeat J-Pop-ish K-pop then there’s this one chill song at the end. Just like on the “Stand Up” mini-album, all K-pop songs, then there’s “Oh My Friend.” It’s one song that completely stands out. Just like DaeSung said during SBS The Big Bang Show…

About to read the article, but BEFORE I do, I’ll give my (very abridged) take: We are definitely not alone in the universe, *probably* not alone in the galaxy — but we’ll never, ever make contact. If we get very lucky, we might find simple life either in the solar system, or possibly with an extra-solar probe, but that’s a long shot.

Both my optimism and pessimism stem from a recognition of the size of the universe. It’s just too big for me to believe we are alone. But it’s also too big to even find our nearest neighbors.

Okay, now having read the article, I find Phil’s thought that we might most likely find evidence of simple life via a telltale signal in a distant planet highly plausible. Of course, would people really be convinced? Or would we think it was still too possible that the excess oxygen was produced be an unknown inorganic process?

In any case, it does not at all change my conviction that we will almost certainly never make contact with other intelligent life. The distances are simply too vast, so unless intelligent life turns out to be remarkably common, we will never even make radio contact.

It is very hard to make probabilistic arguments when your sample size is 1. Many researchers now believe that life as we know it is likely to exist elsewhere in the universe, but no-one in the field of astrobiology will make the unsupportable claim that it definitely does exist.

Basically, there is not enough evidence on which to base such a conclusion.

Personally, I think it highly likely that life resembling bacteria does exist elsewhere in the universe, but that is nothing more than a gut feeling, based on what we know about life and about the ubiquity of exoplanets. It is not science.